This invention relates generally to techniques for reproducibly transferring patterns to semiconductor devices and particularly to techniques which do not require the use of expensive steppers or the like. The techniques have applicability, for example, in connection with the formation of field emission displays.
In the manufacture of most modern semiconductor devices, a pattern is repeatedly transferred to a substrate using a device called a photolithographic stepper. The stepper is a highly precise machine which may use ultraviolet light to transfer an image formed on a glass plate called a reticle or mask to the semiconductor substrate. For example, the image may be transferred by shining light through the stepper reticle which has an enlarged version of the desired pattern formed on it. The light pattern created by the reticle pattern causes the photoresist to be exposed in the desired pattern. Photoresist can then be developed and etched depending on whether or not it was or was not exposed to light. The photoresist etches differently based on light exposure, and therefore the pattern formed on the reticle in the stepper can be accurately transferred to the substrate.
In many instances, it may be necessary to transfer a pattern reproducibly to a substrate, but the degree of precision enabled by modern stepper technology may not be absolutely required. Because higher resolution stepper equipment is extremely expensive especially for large substrates, it would be desirable to develop a process which allows patterns to be transferred without requiring the use of expensive stepper technology.
One such technique is described in an article by Y. Xia, D. Qin and G. Whitesides, "Microcontact Printing with a Cylindrical Rolling Stamp: A Practical Step Toward Automatic Manufacturing of Patterns with Submicrometer Sized Features," Adv. Mater. 1996, 8. No. 12, page 1015. The article describes a surface patterned rolling stamp which transfers ink to selected regions of the substrate surface in a non-random pattern. The ink may be an alkanethiolate printed on evaporated films of gold or silver. Selective wet etching in aqueous ferricyanide solution is utilized to form features in a silver or gold layer formed on a silicon substrate. While this technique may have promise, special materials and layers that may be relatively expensive are utilized.
Field emission displays are a type of flat panel display which may be useful as a display screen for a wide variety of electronic devices. For example, one potential application is to use the field emission display as a display screen for a laptop computer. This would mean that the field emission display would likely be formed on a relatively large substrate. But perhaps more importantly, to form a substrate of this size on a silicon wafer would be expensive. The expense arises as a function of the size of the wafer. Moreover, if photolitographic steppers were utilized to pattern such a large, specially configured substrate, special steppers would be required. This likely would mean additional expense as well.
Thus, there is a continuing need for a way to pattern semiconductors as cost effectively as possible. The need is particularly acute in connection with the fabrication of large field emission displays.